Amazon may be quietly locking out its competition with ebook creation apps like the newly released Kindle Creator, but not all ebook creation apps tie you down to a single distribution channel.
Even iBooks Author can make and export Epub3 files now, and that's not the only app authors can use to make ebooks.
Here's a double handful of apps and online services which can make ebooks (let me know if I missed one you like).
First, here's the free app I use:
Sigil is not the best app on this list but when it comes to free alternatives there is simply no comparison.
I found it easy to learn with an intuitive interface that did everything I wanted, and I am still waiting for a good reason to switch to another app like:
Jutoh is an ebook creation tool for all platforms (including the Raspberry Pi). It can make ebooks in all the popular formats and, aloing with Scrivener, comes highly recommended (although there is a vim/emacs divide in the author cimmunoty over which is better).
Vellum is a macOS-only app which costs so much that I can't come up with a good reason to buy it.
It is a rather expensive app and costs either $200 for an unlimited license or $10 to $30 for each title. That is rather pricey when compared to the free apps much less the paid alternatives like:
Scrivener is the one paid app everyone recommends - including those who don't use it.
It is a complex and feature-rich app which is designed to cover all the steps in the process of creating a book rather than just the act of making an ebook. It has always been way more than what I required, but many authors swear by it.
Calibre is known as the best ebook library tool, free or paid, but it can also make ebooks in just about any format you can name. You can even use it to edit ebooks, although you shouldn't distribute them to other professionals.
While I use calibre to convert ebooks and manage my library, I also know that it is widely hated by many in the digital publishing industry. Calibre makes ebooks which look okay, but the code is absolutely atrocious (Calibre-made ebooks have even been banned by Amazon once or twice).
Calligra is the office suite which used to be known as KOffice way back when. It was originally developed for Linux systems and has since been ported to Windows, macOS, freeBSD.
Calligra has included an ebook export option since 2012, although I am not sure very many people are using it.
eBookBurn is a paid web service I have been meaning to try. It costs $19 to export an ebook in Epub and Kindle formats, but you can set up as many ebooks - or parts of an ebook - as you like.
Do you know how they say that a third of the web runs on WordPress?
That includes Pressbooks. This paid service lets you upload (or type) parts of a book, edit them, and then export an ebook in Epub, PDF, or Kindle format.
Everything except for the last step is free, and you can even set your preferred formatting as CSS. what's more, WP is designed to publish to the web, and Pressbooks takes advantage of this. You like you can upload a book and then show it off and get feedback.